The invention is based on an apparatus having a position actuator, the position of which determines a power of a driving engine, as defined hereinafter.
In a known apparatus in a vehicle, a positioner can be actuated via an accelerator pedal. When the accelerator pedal is not actuated, the positioner rests on a stop. If the accelerator pedal is actuated in the full-load direction, then via the positioner, the throttle valve is likewise adjusted in the full-load direction, after a play between the positioner and a rotary element connected to the throttle valve has been overcome. An arm is also connected to the throttle valve, and a compression spring is disposed between the arm and the positioner. At one end the compression spring presses upon the positioner in the full-load direction, and on the other end it presses upon the arm in the idling direction of the engine. A tension spring acts on the positioner in the direction of reduced engine power. If the accelerator pedal is not actuated or is actuated only a little, the arm rests on a stop of a servo drive. Via the servo drive, the arm and thus the throttle valve can be adjusted in the idling range of the driving engine.
In order that the positioner will not also be adjusted by the servo drive upon the adjustment of the throttle valve, the tension spring must be substantially stronger than the compression spring between the arm and the positioner.
In the event of failure of the compression spring between the positioner and the arm connected to the throttle valve, the throttle valve will assume a floating, indeterminate position, even if the tension spring continues to work properly.
If the servo drive fails in the idling control range of the driving engine, for instance because of an electrical defect, the stop remains in the last position predetermined by the servo drive. In that case the throttle valve can be unpredictably open or widely closed with the accelerator pedal in its nonactuated position, and the driving engine can operate unforeseeably at particularly high rpm, or stall because the throttle valve is open too far, while the accelerator pedal is not actuated.
Since the compression spring is installed between the positioner and the arm, the force to be brought to bear via the servo drive to regulate the idling rpm is dependent on the position of the positioner, as well as on other factors.
The compression spring between the arm and the positioner has the result that the arm connected to the throttle valve and the positioner connected to the accelerator pedal cannot be mounted together in separate component units in a simple manner.